<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .main {
            border: 5px solid #00BCD4;
            overflow: hidden
        }
        
        .left {
            float: left;
            width: 300px;
            height: auto;
            background-color: red;
            color: #fff;
            padding-bottom: 50px;
            margin-bottom: -50px;
        }
        
        .middle {
            float: left;
            width: 100px;
            height: auto;
            background-color: green;
            color: #fff;
            padding-bottom: 9999px;
            margin-bottom: -9999px;
        }
        
        .right {
            float: left;
            margin-left: 300px;
            height: auto;
            color: #fff;
            background-color: blue;
        }
    </style>
</head>

<body>
    <div class="main">
        <div class="left">
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        </div>
        <div class="middle" fsdfsfsdf>
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        </div>
        <div class="right" fsdfsfsdf>
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        </div>
    </div>
</body>

</html>